A soft lining process involves utilising a flexible tube which is sized to the diameter and length of the pipeline or passageway to be lined. The tube is coated or impregnated with a curable synthetic resin which cures after the lining tube has been placed in position lining the surface of the pipeline or passageway in order either to form an adhesive which anchors the lining tube to the pipeline or passageway surface or to form in effect a moulded body defining a rigid pipe which is free standing inside the pipeline or passageway. The lining tube is inserted in the pipeline or passageway whilst the resin is still soft, and is shaped to the passageway surface by fluid pressure, and whilst it is held in this condition the resin is cured usually by the application of heat or more recently by the application of light radiation supplied for example by ultraviolet lights. In the latter case, the resin system chosen has to be activatable by the radiation.
The most widely practised method of soft lining is disclosed in British Patent No. 1449455 and in such method the lining tube is everted into the pipeline or passageway from one end thereof, the lining tube being provided on its outer side with an impermeable coating or film which after eversion becomes the inner surface of the pipelining providing a smooth flow enhancing surface to the interior of the re-lined pipeline or passageway.